Freezing of foods



M. VAN ETTEN FREEZING oF FooDs y April 22, -1947.4

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FREEZING 0F FooDs Filed Oct. 8. 1945 3 Sheets-Sheet 3 MYRoN vm ETTEN Patented Apr. 22, 1947 UNITED s'rArEs PATEsr anais FREEZING F FOODS Myron Van Etten, Salem, Ohio, assignor to The Salem Engineering Company, Salem, Ohio, a

proprietorship Application October 8, 1945, Serial No. 620,943

7 Claims.

This invention relates to the freezing of foods and more particularly to improved methods'and apparatus for accomplishing this function and for effecting the necessary handling of the foods in connection with the freezing process.

, The advantages of quick freezing of foods asv regards the retardation of ice crystallization, of

while the second requires quite complicated and/or extensive apparatus for commercial rates o1' production so that the air blast method is the one most generally accepted. However, the systems heretofore proposed for quick freezing by the latter method entailed poor over-al1 elllciency and diiculty in maintaining the air in the freezing chamber at the desired low temperature. Either the freezing chamber is intermittently opened for partial unloading and loading in which case there is a more or less continuous loss of refrigerated air or the chamber is loaded to capacity in one operation in which case the compressor is overloaded in attempting to maintain the required low temperatures. It is accordingly one of the primary objects of the invention to provide improved methods and apparatus for quickly freezing foods, in commercial quantities, by the chilled air blast principle whereby the eiciency of the freezing plant as a whole is materially increased. The invention accomexchange may be effected to thereby freeze large commercial quantities of food to low'temperao tures in a short period of time. 'I'his involves the stratification of the air flow to insure eillcient distribution of the same and a counterilow ar rangement to insure a fairly uniform distribution of temperature gradients thus eifecting a maximum over-all rate of heat transfer.

Another item of importance in the processing and freezing of foods, particularly fruits and vegetables, is the starting of the freezing operation within the` smallest possible period of time following the peeling and other preparation ci' the food articles so as to minimize decomposition and consequent discoloration. In a, plant having a more or less continuous preparing vline it is desirable that the finished product be charged into the freezer in a substantially continuous manner. "it is therefore another of the primary objects of the invention to provide improved methods and apparatus for quick freezing foods by the chilled air blast principle which methods and apparatus are amenable to rapid intermittent charging without appreciable loss of the deeply chilled air and without interfering withHK the continuation cf'the freezing action' in the freezing chamber. This is accomplished in accordance with the preferred embodiment of the linvention by arranging the food, either packplishes this object while yet providing a practical arrangement'for loading and unloading the freezing chamber and in a representative embodiment of the invention the accomplishment of the ob-l ject results from the employment of an arrangement whereby the freezing chamber proper is -always substantially sealed against the egress or ingress of air and whereby but one of a number of tray racks or supports is ejected from the chamber at any one time for unloading of the frozen product and loading of the unfrozen product.

Another of the more important objects of the invention is the provision in a chilled air blast type of food freezing system of an improved and simplified arrangement of interrelating the food and air streams whereby a maximum rate of heat aged or in bulk, on light metallic trays and simultaneously loading a multiplicity of such filled trays on one of a'number of individual supports or racks which move about in the freezing chainber on a conveyor system which elects only a single support or rack from the chamber at one time for loading and unloading. .It should be observed, further, that this arrangement is also of advantage as regards over-all efficiency of operation since the individual racks are-not out of the freezing chamber a suiilcientglength of time to pick up much heat and consequently the only heat which must-be extracted in the chamber comes from the food and the trays. By constructing the latter .oi very thin material the total heat carried by the metal is small in proportion to the heat carried by the food and the load on the refrigerating system is Aaccordingly diminished.

A further object of the invention is the provision of an improved food freezing system of out being shut down for reconditioning of the.

cooling system. Another advantage sought and provided by the invention is the economical maintaining of the air in the freezing chamber at eiective processing temperature when the freezing load is reduced or withdrawn so that economic stand-by losses in plants of this character may be reduced.

A still further object of the invention is the provision of improved means to support either bulk or packaged food in a chilled air blast freezing chamber and of improvedrneans to charge and discharge the food into and out oi the chamber.

The above and other objects and advantages of the invention will become apparent upon consideration of the following detailed specification and the accompanying drawing wherein there is disclosed a preferred embodiment of the invention.

In the drawing:

Figure 1 is a partial plan view of the food freezing plant constructed in accordance with the principles of the invention;

Figure 2 is a transverse section through the apparatus of Figure l; f

Figures 3 and 4 are side and front elevational views, respectively, of one of the tray racks utilized inthe assembly of Figure 1;

Figure 5 is a side elevation illustrating the loading of trays on one of the racks by means of the tray handling device of the invention; and

Figure 6 is a longitudinal section through the lifting column of the tray handling device of the invention.

In carrying out my invention I construct a refrigerated enclosure having'outer insulated side walls It and a partition wall II dividing the enclosure into two principal roomsthe room I2 for frozen food storage and the room I3 for rapid or deep freezing. Thus, the room I3 will normally be maintained at a much lower temperature than the room i2 and this increased refrigeration will result from the blasts of deeply chilled air which are utilized, ina manner to be hereinafter more fully explained, in the freezing of the .food placed in the room I3. Room I3 is provided with a vestibule I4, the purpose of which will be described in detail below, and with .an outer entrance door l5. A door IS provides access to the space i2 and a .third door Il provides-access to the space it in bypassing relation to the vestibule Id.

Extending along the outer wall of the space it is a number ofair cooling and air moving assemblies IS each having refrigerant evaporating coils i3, a spray head 2li for directing a defrosting liquid onto the coils I9, and a blower 2l for rapn idly moving large volumes of air over the coils It. The fluid employed at the spray heads 22 has such hy'groscopic and low freezing point characa teristics that it is operative to prevent the formation of frost on the coils it and as 'this liquid is recirculated continuously I provide concentrator 22 which operates to take out the water as the same is picked up by the liquid during its passage over the coils le. l

Extending downwardly along the opposite wall of space I3 is a continuous distributing duct 2t having a multiplicity of vertical spaced "out longitudinally extending slit openings 2t through which the chilled air coming into the duct 23 under pressure may be ejected horizontally. The upper portion of duct 23 is connected with a pair of horizontal ducts 25 leading from the outlets of blowers 2l and extending transversely across 4 the roof of the space I3 as shown. To complete the recirculatory path of the freezing air I provide longitudinally extending inlets26 along the bottom of each of the air cooling units I8`.

Extending longitudinally in the chamber I3' intermediate the assemblies I8 and the duct 23 is an endless chain conveyor comprised of the chain 2l and outwardly spaced supporting rollers 28. This conveyor may be of the kind shown in detail ln U. S. Patent No. 2,342,468 but is preferably of the type shown in detail in the co-pending application of Hubert Schebler, Serial No. 475,805, iiled February 13, 1943. Asv such, the endless chain is entrained over a pair of spaced horizontally disposed sprockets one of which is driven by a motor 29. Connected to this. chain along their inner side edges are a plurality of adjacent plates 20 which are supported on the rollers 28 during their travel about the orbital path provided. A suitable indexing control, which may be similar to that shown and described in said ,copending application, may be provided for the rrctor 29 and a control switch 3| may Ibe placed in close proximity to the door I5 so that upon each actuation of the switch 3| the motor 29 will operate to bring the next succeeding support or plate 20 into position in front of the door I5 as will be understood. It is also within the echtemplation of the invention that the control switch may be actuated automatically upon closing of the door I5 so that upon closing of this door the conveyor will be actuated and indexed to bring the next succeeding support or plate before the door.

Referring now to Figures 2, 3 and 4, '1t will be observed that each of the plates 30 supports a rack for retaining a plurality of food holding trays in superimposed vertically spaced relation. Such racks are each comprised of vertically extending side plates 32 tied together with a top plate 33 and having outwardly extending iianges 33 along their rear edges. Welded or otherwise of the food trays as will be understood. To assist in guiding the trays into the racks the cleats 34 are curved downwardly at their front end portions as shown at 35. Secured to the flange 33 of the left side plate of each of the rack units is a strip iii of flexible fabric, preferably of vulcanized rubber, and having their ends rigidly secured to the anges 33 of both the side plates 32 is a pair of diagonal braces 31.

Vestibule I4 has a side wall 38 and rear wall 39 formed with openings 40 to allow passage of the rocks during operation of the conveyor. Extending about the edges of the openings 40 are flexible leavesV 4I which press against the racks and which, in cooperation with the solid side plates or` panels 32 of the racks form an eiiective barrier between the vestibule I4 and the space I3. in this manner the ingress and egress of air into and out ci the freezing chamber I3 during the loading and unloading of the racks is kept to an absolute minimum. The indexing mechanism of the control for the driving motor 29 is so adjusted that the conveyor stops when the side plates or panels of two of the racks are wedged in the iiaps 4I of the openings 40.

To further reduce the refrigeration losses and to speed up the loading and `unloading of thel racks on the conveyor whereby the freezing plant will operate at optimumvlefiiciency and rate of production I provide the` charging and dischargi mechanism now to be described. An elevated mono-rail 42 (Figures l, 5) is incorporated in the ing 5|. Slidably mounted on the sleeve 49 andy packing 5l is a second sleeve 52 which is reduced in internal diameter at its upper end portion to closely t the post 44 above the shoulder 4S. A U-shaped packing 53 is inserted against the internal shoulder of thesleeve 52 so that upon the application of uid pressure to the annular 'space intermediate the packlngs 5l and 53 the sleeve 52 will be elevated with respect to the post 44. A tube 54 is slid over the post 44 and has vits lower end portion enlarged in internal diameter to partially receive the sleeve 52. Thus, upon upper movement of sleeve 52 the tube 54 will also be moved upwardly. The upper end of tube 54 is guided concentrically by a bushing 55 and 54 is free to rotate about post 44 and to have vertical movement with respect thereto but, if desired, the extent of such rotation and move ment may be limited by a spring pressed plunger 56 engaging a recess 51 formed in the side wall of post 44. Fluid'underpressure, preferably hydraulic fluid, may be supplied by a exible conduit 58 connected with bores formed in screw 41 and in the lower end portion of post 44 and leadn ing to the annular space aforesaid. A suitable Afoot valve or hand valve, not shown, is employed to control the flow of uid pressure to the lifting unit.

As shown in Figures 1 and 5, a plurality or forks 59 are secured to the tube 54 in uniform vertically spaced relation and, in practice, this spacing is identical with the spacing of cleats 34 on the rack units previously described. Each of the forks 59 is adapted to support one of the food holding trays, which trays may be, in accordance with usual practice, simply upwardly lipped panels formed of light gauge aluminum or other metal sheets. Such trays may be loaded racks formed by the vertical plates di are now loaded in succession in the manner outlined above and it will be understoodthat the racks will move longitudinally through the freezing chamber ilrst past the air coolers i8 and thence past the out lets in the duct 23.. In this manner the coldest air impinges against the food the freezing ai which is almost completed so that effective term perature gradients are maintained at both the freshly charged and frozen load components thereby insuring a high rate oi total heat er.- traction. When loaded racks begin to come into the vestibule I4 the same are quickly unloaded of their trays by the charging device above described and quickly reloaded with fresh food beu fore the conveyor is again actuated to bring the next succeeding rack before the door l5.

It should be noted that the open nature of the tray supporting racks allows free passage of airk (issuing from the'outlets 24 in the duct 23) over and about the trays supported on the racksthe plates 32 making up the racks being positioned parallel with the direction of air flow when in the freezing chamber. Thehorizontally disposed trays and the vertically `disposed plates stand-by losses are reducedfmaking the methy cd and apparatuspractical for intermittent operation. By providing for the counter-flow of the `food and chilled air stream and for thedivision of the stream between all the food trays in the freezing chamber a high operational eiliclency results.V Also, the vclosed vand relatively small freezing4 chamber further reduces 'the refrigerating load.

either with bulk or packaged foods and placed` on the forks 59 ata loading station shown schematically at 60 in Figure 1. The car 43 carrying the forks and trays might now be moved into vestibule lll and assuming that an'ernpty rack is in the vestibule the trays on the forks 59 may be simultaneously charged into such rack. For this purpose fluid pressure is admitted into the lifting mechanism to raise the tube 54 and the trays carried thereby so that the side edges of the trays will enter freely between the cleats 34. Upon the trays being properly positioned horizontally the fluid pressure is released andthe forks moved downwardly free of trays while the side edge portions of the trays rest on the cleats as will be understood. To limit the inward movement of the tray conveyor whereby the trays will be automatically supportedY in proper position relative to the racks I provide a resilient stop or bumping member as shown at 6l in Figure 5.

In operating the plant above described, refrigerant from a suitable compressor, not shown, is supplied to the coils i9 while suitable frost preventing fluid is pumped to the spray heads 2li. The blowers 2l are in continuous operation. The

lil)

The methods and apparatus herein proposed are adaptable to many products, including the hardening of ice cream whether the products be packaged or in bulk and this flexibility is of extreme advantage in many instances.

The aboveV specifically described embodiment ofV the invention should be considered as illustrative only as obviously many changes may be made therein without departing from the spirit or scope of the invention. Reference should therefore be lhad to the appended claims in determining the scope of the invention.

Whatlclaim is:

1. Apparatus for tha'duickfreezing of foods comprising in combination a freezing chamber and means to circulate therein a chilled quantity of air, anendless conveyor in said chamber hav..

i ing a loop extending outside said chamber for moving and supporting a plurality of traysup porting racks each adapted to support a multiplicity of food-carrying trays, a pairof adjacent openings in a wall of said chamber vthrough which the conveyor passes and which permits egress and ingress of said racks whereby at least one ol said racks may be moved to a loading position outside said chamber during a period of movement of said conveyor, and means to automatically seal said openings against ingress or egress oi air when said one of said racks is in said loading position.

characterized in that said conveyor comprises a plurality of supports each mounting one of said racks and movable in a horizontal plane along an oval path of travel, said means to circulate being operative to direct the chilled air laterally across the principal direction of movement of said racks, and each of said racks being laterally open to allow free passage therethrough of sai chilled air. 3. Apparatus for the quick freezing of foods comprising in combination an elongated freezing chamber having air cooling and 'air moving means extending longitudinally alongone side wall of said chamber, said means having a longitudinally extending air inlet positionedtoward the bottom l thereof and a longitudinally extended air outlet in the top thereof, anair distributing duct positioned along the opposite side wall of said chamber and having a plurality of vertically spaced but longitudinally extending slit openings to direct chilled air transversely across said chamber, overhead duct means interconnecting said outlet and said distributing duct, a rack mounted for movement longitudinally in said chamber and adapted to support a plurality of vertically spaced food carrying trays, a conveyor to move said rack through said chamberI along al path extending first parallel with and adjacent to said moving means and thencev in an oppOsite direction parallel with and adjacent to said distributing duct.

4. Apparatus for the quick freezing of foodscomprising in combination an elongated freezing chamber having air cooling and air moving means extending longitudinally along one side wall of said chamber, said means having a longitudinally extending air inletpositioned toward the bottomthereof and a longitudinally extending air outlet in the topthereof Lwhereby the air discharged by said means may travel laterally across the upper portion of said chamber, means extending along the opposite side wall of said chamber to direct said discharge air flow downwardly along said opposite side wall, a, conveyor positioned in said chamber -below the path of flow'of said discharge air across the upper portion of said chamber and having a pair' of straight portions disposed in side-by-side relation intermediate said side walls and substantially parallel thereto and having a return bend at one end of said straight portions, A

and a plurality of vertically disposed open-sided racks mounted on said conveyor and each supporting a plurality of horizontally disposed but vertically spaced food-carrying trays.

5. Apparatus for the quick freezing of food comprising in combination a freezing chamber, an air circulating means within said chamber for directing a wide stream of refrigerated air in a path across the upper portion of said chamber, means for deiiecting said stream downwardly along a side wall of said chamber, said circulating means comprising means to draw said stream across the lower portion of said chamber, a conveyor positioned in said chamber below the path of iiow of said air across the upper portion of said chamber and having a pair of straight portions disposed in side-by-side relation substantially parallel to said wall and having a return bend at one end of said straight portions, a plurality of vertically disposed yopen-sided racks mounted on said conveyor and each having a plurality of horizontally disposed but vertically yspaced tray-supporting shelves therein, and a separable food retaining tray slideably received in each of said shelves.

6. Apparatus for the quick freezing of foods comprising in combination an insulated enclosure having a freezing chamber and a vestibule therein, means to circulate chilled air in said freezing chamber, an endless conveyor positioned principally in said chamber but having a portion extending out into said vestibule, a plurality of traysupporting racks carriedby said conveyor and each adapted to support a multiplicity of horizontally disposed but vertically spaced food carrying trays, a pair of adjacent openings in the wall between said vestibule and said chamber through which the conveyor passes and which permits egress and ingress of said racks, means to seal said openings against ingress or egress of air, a door in an outer wall of said vestibule having a width and height complementary to a crosssectional area of one of said racks whereby a full rack charge of food to be frozen may be passed into said vestibule and then into said freezing chamber as a unit.

7. Apparatus for the quick freezing' of foods comprising in combination a freezing chamber and -means to circulate therein a chilled quantity of air, an endless conveyor in said chamber having a loop extending outside said .chamber for moving and supporting a plurality of tray supporting racks each adapted to suppbrt a multiplicity of food-carrying trays, a plurality of traysupporting racks on said conveyor and each having at least one solid vertically extending panel member, a pair of adjacent openings in a wall of said chamber through which the conveyor' passes and which permits egress andA ingress of said racks whereby said racks may be moved in succession to a loading position outside said chamber, said openings being generally complementary in size and shape with said panel members and said racks being so spaced on said conveyor that the panel members of two of said racks are positioned in' said openings to form barriers against the passage of air through said openings when said conveyor is stopped in proper position.

MYRON VAN E'I'IEN.

REFERENCES orrsn The following references are of record in the ille of this patent:

UNTED STATESv PATENTS 

